1. Field of the Invention
This invention relates to a method for operation of an air cleaner used in motor vehicle.
2. Description of the Prior Art
A method for operation the an air cleaner of prior art is as follows:
When an engine of a motor vehicle runs, a blower motor of the air cleaner provided to the motor vehicle is turned on or off in response to a manually operational switch. When the engine is stopped, the blower motor is turned off even if the manually operational switch indicates running state of the blower motor by detecting that rippled components in a supply voltage of the blower motor are lower than a given level. When the engine runs, a dynamo produces electric power, so that the supply voltage contains ripple components because a rectified alternate component developed by the dynamo or noise components developed with commutating is superimposed on an output voltage of a battery. However, when the engine does not run, the ripple component due to running of the dynamo is not developed. Therefore, the blower motor of the air cleaner can be turned off automatically by detecting absence of the ripple component for saving battery power. However, there is a drawback that if a blower motor with larger capacity is used, greater ripple components in the supply voltage are developed because noise components generated with commutation of the blower motor is large. As the result, stop page of the engine cannot be detected because the ripple component does not sufficiently decrease even if the dynamo stops, as shown in FIG. 6. Thus, the blower motor cannot be turned off automatically after engine stop page.